Cell Energetics: Photosynthesis & Respiration

Carbon• Carbon forms millions of compounds, both simple

and complex• All living things contain carbon• Living things cycle carbon from the air (inorganic gas

form) to the solid form (organic) and back to the air• Light from the sun provides the energy for

photosynthesis, the process of making organic compounds such as sugar

• The sun’s energy is stored the chemical bonds of sugars and other carbohydrates

• Carbohydrates are used by most living things to provide energy for LIVING

What is the Global Carbon Cycle?

• The movement of carbon between the atmosphere, soil, ocean, living things, and fossil fuels

• Carbon exists primarily as:- Gas, carbon dioxide (CO2), in Earth’s atmosphere - Organic carbon in living and dead organisms.

• Atmospheric carbon is constantly recycled, mostly by green plants and algae, to produce oxygen

The Global Carbon Cycle

CO2 & other greenhouse

gases

Dissolved carbon

Fossil fuel

Green plants

Algae & cyanobacteria

Emissions from burning fossil fuel

respira

tion

Phot

osyn

thes

is

Photosynthesis and Respiration in the Global Carbon Cycle

Carbohydrates&

Oxygen

Carbon dioxide&

Water

PhotosynthesisRespiration

Creates storedEnergy-ATP

A few types of organisms do not need sunlight and photosynthesis as

a source of energy.

• Some organisms live in places that never get sunlight.

• In chemosynthesis, chemical energy is used to build carbon-based molecules.– similar to photosynthesis– uses chemical energy

instead of light energy– occurs where light cannot

penetrate-deep ocean Biology-McDougal Littell 2008

A cell has some remarkable organelles!!! Is this plant or animal?

Chloroplasts

Mitochondrion

Nucleus

The Chloroplast is Remarkable Organelle

Stroma

Thylakoid

Stroma = space/matrix inside the chloroplast where carbohydrate is synthesized

Thylakoid = structures with chlorophyll and light reaction center

The Basic Process of Photosynthesis

CO2 + H2O [C6H12O6] + O2

carbon dioxide water carbohydrate(glucose)

oxygen

light energy

The Light Reactions-Light Dependent

The Dark Reactions-Light Independent

Photosynthesis in chloroplast is divided into…

The Light Reactions-Light Dependent

The Dark Reactions-Light Independent

MUST occur in the presence of light

CAN occur in the presence of light, but works better in the dark

Keeping track of the oxygen atom in photosynthesis

CO2 + H2O [CH2O] + O2

carbon dioxide water carbohydrates oxygen

light energy

Cornelius van Niel (1897-1985)Standford University

Used radioactive-labeled oxygen in water and unlabeled carbon dioxide in photosynthesis experiments

Found that oxygen gas produced comes from water

Postulated that the oxygen atom in carbohydrates must be from carbon dioxide

The Light Reactions

The Dark Reactions

ADP NADP+ NADPH

Carbohydrates CO2 + H2O

H2O O2

ATP

MC.3.B.4

Where do the reactions happen inside the chloroplast?

Light reactionDark reaction

H2O

O2

CO2

Carbohydrates

Light reaction occurs on thylakoid membranes

Dark reaction occurs in the stroma

MC.3.B.4